A severe weather warning has been issued for Sydney, the Hunter and Illawarra regions, with damaging winds of up to 90kmh and heavy rainfall predicted.
A trough extending from a deepening low pressure system is expected to intensify on Friday and move from the NSW south coast to the north, according to the Bureau of Meteorology.
It will bring with it winds averaging 55-65kmh, with gusts of 90kmh.
There is the possibility of thunderstorms and localised heavy rain, particularly in the Illawarra region, which may lead to flash flooding.
Dangerous surf conditions will also develop in those coastal areas on Friday.
The SES advises that people should stay away from floodwater, keep clear of fallen power lines and move vehicles under cover.
